One method for objectively recreating the evolution of animals is observing the aggregate replacement of DNA sequences and depicting the phylogenetic tree (molecular phylogeny). This method is not always perfect, however. Comparing animals regarding the formation and role of their cells and genes operating at ontogenesis, and gaining an understanding of their ancestors is important for reconstructing animal evolution.
The ancestors of spiders and flies branched off when arthropoda first appeared. Both animals have the common genes for creating their backs, but the nature of the cells in which those genes function differs greatly. What was preserved and what changed from the arthropoda's common ancestors? The clues have now become discernible. |
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| The spider protecting its eggs |
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Biohistory Jyournal, Autumn, 2004
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